Phase III TRYBECA-1 Trial Shows Eryaspase Fails to Improve Survival in Advanced Pancreatic Cancer
Key Insights
The TRYBECA-1 phase III trial of 512 patients found that adding eryaspase to second-line chemotherapy did not significantly improve overall survival in advanced pancreatic ductal adenocarcinoma (search) (7.5 vs 6.7 months; HR 0.92; P=.374).
Despite achieving robust pharmacodynamic target engagement with sustained asparagine depletion and trough asparaginase activity exceeding 500 U/L, the metabolic approach failed to translate into clinical benefit.
The study provides contemporary benchmarks for second-line treatment options in PDAC (search), with disease control rates numerically higher with eryaspase (57.6% vs 49.0%; P=.047) but no improvement in progression-free survival or objective response rates.
The international phase III TRYBECA-1 trial has delivered disappointing results for eryaspase, a red blood cell-encapsulated asparaginase designed to target metabolic dependencies in pancreatic ductal adenocarcinoma (search) (PDAC (search)). The study of 512 patients failed to demonstrate improved survival when eryaspase was added to standard second-line chemotherapy, despite achieving robust pharmacodynamic activity.
Primary Endpoint Missed Despite Metabolic Target Engagement
The trial randomized patients between September 2018 and December 2020 to receive either eryaspase plus chemotherapy (n=255) or chemotherapy alone (n=257). Median overall survival was 7.5 months (95% CI, 6.5-8.3) with eryaspase combination versus 6.7 months (95% CI, 5.4-7.5) with chemotherapy alone, yielding a hazard ratio of 0.92 (95% CI, 0.76-1.11; P=.374).
The negative result occurred despite clear evidence of pharmacodynamic target engagement. Median trough asparaginase activity exceeded 500 U/L—well above the 100 U/L threshold considered pharmacologically active. Plasma asparagine levels fell sharply after eryaspase administration and remained well below baseline throughout treatment, confirming sustained asparagine depletion as intended by the metabolic targeting approach.
Secondary Endpoints Show Limited Clinical Activity
Progression-free survival showed no statistically significant improvement, with median PFS of 3.7 months (95% CI, 3.4-4.1) versus 3.4 months (95% CI, 2.0-3.7) for chemotherapy alone (HR 0.88; 95% CI, 0.73-1.07; P=.196). Independent radiology review confirmed these investigator-assessed findings.
Objective response rates were numerically higher but not statistically significant at 16.1% versus 12.5% (odds ratio 1.35; 95% CI, 0.81-2.24; P=.242). Disease control rate showed the only statistically significant difference, favoring eryaspase at 57.6% versus 49.0% (P=.047), though duration of response remained similar at approximately 5.7-5.8 months in both arms.
Treatment Regimens and Patient Population
The study enrolled adults with histologically confirmed, unresectable stage III/IV PDAC (search) with measurable disease after progression on first-line therapy. Patients had ECOG performance status 0-1 and received investigator's choice of second-line chemotherapy: either gemcitabine (1,000 mg/m²) plus nab-paclitaxel (125 mg/m²) on days 1, 8, 15 of 28-day cycles, or irinotecan-based therapy on days 1 and 15.
Eryaspase was administered at 100 U/kg intravenously on days 1 and 15 of each 28-day cycle. Treatment continued until disease progression, unacceptable toxicity, or patient withdrawal.
Safety Profile Shows Increased Toxicity
Nearly all patients experienced treatment-emergent adverse events, with grade ≥3 events somewhat more frequent in the eryaspase arm. Notable grade ≥3 events included neutropenia (25.4% vs 20.3%), asthenia (16.9% vs 13.8%), and anemia (17.3% vs 12.2%).
Treatment-emergent adverse event-related discontinuations occurred in 18.5% versus 16.7% of patients. Fatal treatment-emergent adverse events occurred in 5.6% versus 3.7% of patients, with study drug-related deaths in 1.6% versus 0.8%.
The most common adverse events of any grade were asthenia (75.4% vs 70.7%), diarrhea (55.6% vs 45.5%), and anemia (51.6% vs 40.7%). The safety profile was otherwise consistent with expectations for the respective chemotherapy backbones.
Immunogenicity and Biomarker Insights
Neutralizing anti-asparaginase antibodies were detected post-baseline in 68.5% of eryaspase-treated patients, though trough asparaginase activity generally remained above the pharmacologic threshold. Exploratory analyses suggested that deeper asparagine depletion (nadir <15 μmol/L) might be associated with better overall survival within the eryaspase/irinotecan/5-FU subgroup (HR ~0.58), though this requires further validation.
Clinical Context and Implications
PDAC (search) remains one of the most lethal cancers, with a global 5-year survival rate near 10%. After progression on first-line regimens such as FOLFIRINOX, NALIRIFOX (search), or gemcitabine/nab-paclitaxel, only about half of patients are fit enough for second-line therapy. The metabolic rewiring driven by ubiquitous KRAS (search) mutations creates dependencies on amino acids such as asparagine and glutamine, providing the rationale for eryaspase development.
The trial provides large, contemporary benchmarks for gemcitabine/nab-paclitaxel and irinotecan-based regimens in the second-line PDAC (search) setting. However, the failure to translate robust pharmacodynamic activity into clinical benefit underscores the need to pivot toward biomarker-driven and mechanism-based combinations that target PDAC's fundamental oncogenic and microenvironmental biology.
As the investigators concluded, "These results do not support additional development of eryaspase in pancreatic cancer (search)," highlighting the ongoing challenge of improving outcomes in this devastating disease despite achieving clear target engagement with novel metabolic approaches.